Discussion:
Strange USB-Audio streaming behaviour of DPC
(too old to reply)
MichaelS
2010-05-25 20:13:01 UTC
Permalink
I am running up to 6 USB audio devices (8bit 8khz sampling rate) in parallel
and I have observed on my computer, that DPC starts with a CPU load of 35-50%
and after 2 minutes the CPU load decreases down to 0%.

However, sometimes the DPC pulses in the following way:
* 5 seconds no CPU load
* 3 seconds 20-30% CPU load.

I am not sure what could cause such an effect and until now I have tried
different configurations without a hint. However, the USB host controller
should not be a bottleneck. I have a load of less than 5% of total USB
bandwidth.

Environment:
* Windows 7 64bit
* HP xw4600 workstation
* up to 6 USB audio devices connected over a hub

Can anyone gives me hint?
g
michael
Philip Ries [MSFT]
2010-05-26 18:10:40 UTC
Permalink
Sounds similar to this issue (hotfix available):

http://support.microsoft.com/kb/981214
Post by MichaelS
I am running up to 6 USB audio devices (8bit 8khz sampling rate) in parallel
and I have observed on my computer, that DPC starts with a CPU load of 35-50%
and after 2 minutes the CPU load decreases down to 0%.
* 5 seconds no CPU load
* 3 seconds 20-30% CPU load.
I am not sure what could cause such an effect and until now I have tried
different configurations without a hint. However, the USB host controller
should not be a bottleneck. I have a load of less than 5% of total USB
bandwidth.
* Windows 7 64bit
* HP xw4600 workstation
* up to 6 USB audio devices connected over a hub
Can anyone gives me hint?
g
michael
MichaelS
2010-05-27 20:16:39 UTC
Permalink
Tests have been successful. Now, I cannot observe the DPC pulse.

However, after initiating streaming the DPC starts with a constant CPU load
of 20-30% and decreases after 2 minutes.
g
Michael
MichaelS
2010-05-27 22:00:32 UTC
Permalink
Thanks for the hint. I will install the hotfix.
However, most of the audio devices are USB1.1 devices which are connected to
a USB 2.0 MTT capable hub.
g
Michael
Post by Philip Ries [MSFT]
http://support.microsoft.com/kb/981214
Post by MichaelS
I am running up to 6 USB audio devices (8bit 8khz sampling rate) in parallel
and I have observed on my computer, that DPC starts with a CPU load of 35-50%
and after 2 minutes the CPU load decreases down to 0%.
* 5 seconds no CPU load
* 3 seconds 20-30% CPU load.
I am not sure what could cause such an effect and until now I have tried
different configurations without a hint. However, the USB host controller
should not be a bottleneck. I have a load of less than 5% of total USB
bandwidth.
* Windows 7 64bit
* HP xw4600 workstation
* up to 6 USB audio devices connected over a hub
Can anyone gives me hint?
g
michael
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